Why does my \hbar look like this?

Question

This \hbar is ugly with the bar too high and too left

This is what I want

My settings are:

\documentclass{beamer}
\usetheme{default}
\usecolortheme{seahorse}
\setbeamertemplate{navigation symbols}{}
\setbeamertemplate{items}[ball]
\setbeamertemplate{footline}[frame number]
\setbeamertemplate{section in toc}[ball]
\setbeamerfont{section in toc}{series=\bfseries}
\renewcommand{\arraystretch}{1.25}

\usepackage[fontset=none]{ctex}
\setCJKsansfont{SimSun}[BoldFont=Noto Sans CJK SC Medium]
\usepackage{amsmath,amssymb,mathrsfs,bm}
\usepackage{tikz}
\usepackage{anyfontsize}
\usepackage{fontspec}
\usefonttheme[onlymath]{serif}
\usepackage{color}
\usepackage{graphicx,caption,subcaption}
\usepackage{hyperref}
\hypersetup{
    colorlinks=true,
    linkcolor=blue,
    filecolor=green,
    urlcolor=cyan,
    citecolor=cyan,
}

\AtBeginDocument{
  \let\uglyepsilon\epsilon
  \renewcommand\epsilon{\varepsilon}
}
\AtBeginDocument{
  \let\uglymathsf\mathsf
  \renewcommand\mathsf{\symsf}
}

\let\sectiononly\section
\renewcommand{\section}[1]{
    \sectiononly{#1}
    \let\sectiontitle\relax
    \newcommand{\sectiontitle}{#1}
}

\newenvironment{slide}{
    \begin{frame}{\bfseries{\sectiontitle}}
}{
    \end{frame}
}

what is next is: if I add:

\usepackage{unicode-math}
\unimathsetup{bold-style=ISO, mathrm=sym}
\setmathfont{Latin Modern Math}
\renewcommand{\bm}{\symbf}

to my settings, it will look like this:

Answer 1

unicode-math by default uses Latin Modern Math as the math mode font which is why the \hbar looks different. To access the original Computer Modern \hbar you can do something like this.

\documentclass{article}
\usepackage{mathtools, amssymb}
\let\oldhbar\hbar % Computer Modern hbar
\usepackage[warnings-off={mathtools-colon,mathtools-overbracket}]{unicode-math} % Math fonts
\setmathfont{Latin Modern Math}
\let\newhbar\hbar % Latin Modern hbar

\begin{document}
\def\hbar{\oldhbar\mkern1mu} % hbar kerning redefinition
\[\hbar\]
\end{document}

Hope this helps.